This invention relates to improvements in machines for mass producing containers such as metal cans. In the mass production process currently employed, pre-sized sheets of metal are generally formed into hollow, cylindrical container bodies with the facing longitudinal edges of each body defining an interlocking seam. The seam is typically sealed with airhardened molten material such as solder, and thereafter the excess solder is generally removed by physically wiping the seam with an appropriate buffer.
In modern can fabricating systems, the manufacturing process is virtually completely automatic. Moreover, it is not uncommon for such systems to produce cans at a prodigious rate, one system operating at the remarkable speed of about 425 cans per minute. Such high speed systems generally require that the container bodies be transported to and from the various fabrication stations at closely-spaced intervals.
Though the close spacing of the container bodies contributes to the prodigious rates of can production, it is not without concomitant problems. In particular, during the fabrication sequence when excess solder is removed by physically wiping the seam with an appropriate buffer, the molten, or quasi-molten solder material is automatically thrown from the seam in a somewhat indiscriminate manner. Some of this solder material, sometimes referred to as "tramp lead" because solder generally consists, at least partially of lead, is directed toward the container bodies immediately following or preceding the particular body being wiped. Since, at this stage of the fabrication process, ends have not yet been secured to the container bodies, some of this tramp lead lands, and hardens, on the interior walls of the container bodies. Lead-containing solder is, of course, a toxic material, and therefore this is a very undesirable result, particularly when the completed cans are filled with food for human consumption.
In the past, a number of methods have been employed to prevent tramp lead from landing inside the container bodies. These methods have included attempts to intermittently move a shield-like article between adjacent container bodies during the wiping sequence. Such shields have typically been moved into position through means of a moving belt, gears and the like. Unfortunately, these prior attempts have not met with great success.
Accordingly, it is a primary object of this invention to provide an improved can fabricating system which effectively prevents tramp lead and other spurious substances from landing inside container bodies during the seam-wiping sequence previously described. The improved system does not reduce the relatively high rate of can production achieved heretofore, yet it can be installed in existing can fabrication machinery with only minimal modifications.
It is another object of the invention to provide an improved article of manufacture for shielding the interior of each of a succession of container bodies from impurities present during the fabrication process, and to further provide an improved can fabricating process for effectively minimizing the amount of impurities which may land inside a container body during fabrication thereof. Other objects, features and advantages of the invention will be apparent hereinafter.